Preheat oven to 325°F with rack set in the center of the oven.
Generously spray a 7x2-inch nonstick round cake pan with nonstick cooking spray.
Line the bottom of pan with a parchment paper circle, spray parchment paper circle with cooking spray.
Coat bottom and sides of pan with flour, tapping out excess.
Roughly chop almonds and hazelnuts and place in a large, wide bowl, along with orange peel, apricots, and figs; toss to combine.
In a medium bowl, whisk together flour, cinnamon, cocoa powder, salt, nutmeg, cloves, and pepper.
Add to bowl of nuts and fruit and toss until well combined.
Place sugar, honey, and butter in a medium saucepan over medium heat.
Cook mixture until it reaches 238-240°F on an instant-read or candy thermometer.
Remove pan from heat and quickly pour sugar mixture into nut mixture.
Stir until well combined, using a wooden spoon.
Transfer mixture to prepared cake pan, pressing lightly (damp hands) and smoothing surface with a spatula.
Transfer cake pan to oven and bake until about 2-inches of the outer edge is bubbling, 35 to 45 minutes.
Transfer cake to wire rack and let cool about 1 hour; run a warm, damp knife around edge to loosen.
Cool for an additional 15-30 minutes, run a damp knife around edge of pan again and invert over rack (smack pan bottom) to remove from pan; turn cake over again (bumpy top up) and cool completely (pull parchment off bottom while still barely warm).
Wrap well with plastic wrap, parchment paper, and then again with plastic wrap.
Store in a cool, dry place at least one week before serving; panforte keeps well at least 3 months.
To serve, dust the panforte with confectioners' sugar, if using, and cut into thin wedges with a sharp knife.